Eating late at night increases the risk of heart disease and diabetes by raising levels of harmful blood fats, warns new research.
Shift work, in particular, is triggering the killer illnesses by leading to people eating their meals at the wrong time of day, according to the study from the National Autonomous University of Mexico.
Scientists found jet lag, or simply staying up, is also dangerous by leading to midnight suppers.
Experiments on rats found when they ate at the start of their rest period there was a dramatic spike in triglycerides, compared to being fed just before they became active.
Nighttime eating is closely linked to high levels of triglyceride in the blood, which elevates the risk of developing heart disease and diabetes, new research shows
Triglycerides are blood fats produced in the liver and derived from foods such as meat, dairy products and cooking oils.
They are different from cholesterol but can also clog arteries, leading to cardiovascular disease, or inflame the pancreas, triggering diabetes.
Previous research has found people with high levels of triglycerides in their blood are more likely to have heart problems.
The latest findings, published in the journal Experimental Physiology, suggest that the body’s 24 hour cycle is to blame.
When the part of the rat’s brain that controls the ‘body clock’ – or circadian rhythm – there was no longer a change in fat levels.
Cardiovascular disease and diabetes are linked to a lifestyle where humans ignore the signals of the biological clock – and eat in the evening and late at night.
The researchers said the study demonstrates why such a routine is out of sync with our 24-hour cycle and may result in high blood fat levels – and thus a higher risk for illness.
Study author Dr Ruud Buijs said: ‘The fact we can ignore our biological clock is important for survival.
‘We can decide to sleep during the day when we are extremely tired, or we run away from danger at night.
‘However, doing this frequently – with shift work, jet lag, or staying up late at night – will harm our health in the long term especially when we eat at times when we should sleep.’
Earlier this year, a study by US scientists found people put on more weight when they ate three meals a day between noon and 11pm than when they consumed the same amount of calories from 8am to 7pm.
The late night meals caused them to pile on the pounds by reducing their body’s metabolism – the process by which fats are broken down and used for energy.
Delayed eating also led them to store carbohydrates – which can lead to weight gain – and raised blood sugar and insulin levels, increasing the risk of diabetes. Their cholesterol and triglyceride levels rose too, raising the likelihood of heart disease.
Dr Buijs explained energy metabolism follows a daily, or ‘diurnal’ pattern, mainly driven by the SCN (Suprachiasmatic nucleus), a tiny region of the brain that regulates the body clock.
‘Disruption of circadian regulation has been linked to metabolic abnormalities,’ he said.
‘Indeed, epidemiological evidence shows night work is a risk factor for cardiovascular disease.’
As rats are nocturnal, they rest during the day and are active at night. When they ate two hours after the onset of daylight, rather than dark, their triglyceride levels soared.
Dr Buijs: ‘These findings show the SCN has a major role in day-night variations in plasma triglycerides by promoting their uptake into skeletal muscle and brown adipose tissue.
‘Consequently, disturbance of the biological clock might be an important risk factor contributing to the development of hyperlipidemia (high blood fats).’
He said the SCN is at the base of the anterior hypothalamus and is ‘the master pacemaker of the circadian system.’
In the last decade studies have documented triglycerides can cause strokes and heart attacks.
In humans they rise during the resting phase, suggesting the involvement of the SCN on behavioral activity.
Added Dr Buijs: Moreover epidemiological studies show that night workers, who have activity and meal patterns shifted towards the night have an increased risk for cardiovascular diseases.’
Since rodents are nocturnal animals the day results of these animals is ‘thought to be equivalent to night in humans.’
Dr Buijs said: ‘Thus, this day-night variation in triglyceride metabolism provides a possible explanation for the increased risk of cardiovascular diseases seen in night workers who have shifted meal patterns towards the night.’
‘Since triglyceride levels are an important factor in the progress of blood clots, these results may have potential implications for the cause of cardiovascular diseases in the context of inadequate feeding times, shifted towards the rest phase, that commonly occur in westernized countries – late night dinners – and in night workers.’
According to a 2013 study early eaters lost approximately 12 percent of their body weight, while late eaters lost only 8 percent, even though they all followed the same diet and exercise regime.
And according to a 2007 study people who eat most of their food at night have higher body mass indexes than those who eat earlier in the day.
Another study showed participants who ate between 11 pm and 5am gained more weight than those who did not eat during those hours.